1. Field
The presently disclosed subject matter relates to semiconductor light-emitting devices, and more particularly to surface mount semiconductor light-emitting devices having a double encapsulating structure, which can have favorable optical characteristics by forming a first encapsulating material in a substantially fair dome shape when a semiconductor light-emitting chip is encapsulated by the first encapsulating material.
2. Description of the Related Art
In various semiconductor light-emitting devices, surface mount light-emitting devices are frequently used for an electronic device such as a mobile phone, a personal computer and the like because they are small and can be directly mounted along with other electronic parts on a mounting circuit board in a reflow soldering process. Conventional semiconductor light-emitting devices of a surface mount type, for example, are disclosed in Patent Document No. 1 (Japanese Patent Application Laid Open JP2003-282952) and No. 2 (U.S. Pat. No. 8,115,106).
FIGS. 9a and 9b are an enlarged top view and an enlarged side cross-sectional view showing a first conventional semiconductor light-emitting device of the surface mount type, which may improve a reliability and may be miniaturized as a light source for a back light unit of an liquid crystal display (LCD) apparatus and the like and which is disclosed in Patent Document No. 1, respectively.
The first conventional semiconductor light-emitting device 70 includes: a circuit board 80 having a first end and a second end; a first conductor pattern 81 having a first external electrode 81a and a die-bonding pad 81b formed on the circuit board 80 and extending from the first end of the circuit board 80 toward a middle portion of the circuit board 80, the first external electrode 81a extending along the first end of the circuit board 80, and the die-bonding pad 81b extending from the first external electrode 81a toward the middle porting of circuit board 80; a second conductor pattern 82 having a second external electrode 82a and a wire-bonding pad 82b formed on the circuit board 80 and extending from the second end of the circuit board 80 toward the middle portion of the circuit board 80 so as not to contact with the die-bonding pad 81b, the second external electrode 82a extending along the second end of the circuit board 80, and the wire-bonding pad 82b extending from the second external electrode 82a toward the middle porting of circuit board 80; and wherein the first external electrode 81a of the first conductor pattern 81 and the second external electrode 82a of the second conductor pattern 82 are used to receive a power supply.
In addition, the first conventional semiconductor light-emitting device 70 also includes: a semiconductor light-emitting chip 83 having a first top electrode and a second top electrode mounted on the die-bonding pad 81b; a first bonding wire 84a electrically connecting between the first top electrode of the semiconductor light-emitting chip 83 and the die-bonding pad 81b of the first conductor pattern 81; a second bonding wire 84b electrically connecting between the second top electrode of the semiconductor light-emitting chip 83 and the wire-bonding pad 82b of the second conductor pattern 82; a first encapsulating resin 85 being composed of a transparent silicone resin, covering each of contact portions between the first top electrode of the chip 83 and the first bonding wire 84a and between the second top electrode of the chip 83 and the second bonding wire 84b, and encapsulating the semiconductor light-emitting chip 83 so as to be formed in a dome shape; and a second encapsulating resin 86 being composed of a transparent epoxy resin, encapsulating the first encapsulating layer 85 along with parts of the first and the second bonding wires 84a and 84b exposed from the first encapsulating resin 85, and being formed in a cubic shape on the circuit board 80.
When the semiconductor light-emitting chip 83 is encapsulated by the first encapsulating resin 85 in manufacturing processes for the conventional semiconductor light-emitting device 70, a predetermined amount of an uncured first encapsulating resin may be dropped from an upward direction of the semiconductor light-emitting chip 83 toward the chip 83 and may cover the semiconductor light-emitting chip 83 including each of the contact portions between the first top electrode of the chip 83 and the first bonding wire 84a and between the second top electrode of the chip 83 and the second bonding wire 84b in the dome shape therewith. After that, the first encapsulating resin 85 may be formed by heat-solidifying the uncured first encapsulating resin.
In this case, with reference to a central axis X of the chip 83, a first distance D1 of the die-bonding pad 81b between the central axis X of the chip 83 and an end 81ba of the first external electrode 81a of the first conductor pattern 81 differs from a second distance D2 of the die-bonding pad 81b between the central axis X of the chip 83 and an end 81bb of the die-bonding pad 81b of the first conductor pattern 81. Specifically, the first distance D1 is longer than the second distance D2 of the die-bonding pad 81b as shown in FIG. 9a. 
Accordingly, the uncured first encapsulating resin, which is dropped from the upward direction of the semiconductor light-emitting chip 83 toward the chip 83 mounted on the die-bonding pad 81b so as to cover the semiconductor light-emitting chip 83 in the dome shape, may spread under wet conditions on the die-bonding pad 81b toward the first external electrode 81a. By contrast toward the first external electrode 81a, the spread under wet conditions of the uncured first encapsulating resin toward the second external electrode 82a may be stopped by the end 81bb of the die-bonding pad 81b. 
As a result, the first encapsulating resin 85, which should be formed in a dome shape, may not become symmetric with reference to the central axis X of the semiconductor light-emitting chip 83, which is die-bonded on the die-bonding pad 81 of the first conductor pattern 81. That is, the first encapsulating resin 85 may be subject to an off-center arrangement with reference to the central axis X of the chip 83, and also the dome shape of the first encapsulating resin 85 may be variable when the conventional semiconductor light-emitting device 70 is manufactured in a mass production process.
The above-described variability of the dome shape of the first encapsulating resin 85 may cause variabilities of optical characteristics such as directional characteristics, when light emitted from the semiconductor light-emitting chip 83 transfers in the first encapsulating resin 85 and enters into the second encapsulating resin 86. Additionally, the variability of the dome shape of the first encapsulating resin 85 may also cause the variabilities of the optical characteristics such as the directional characteristics, when light emitted from the first encapsulating resin 85 transfers in the second encapsulating resin 86 and is emitted in an outward direction of the semiconductor light-emitting device 70. Thereby, the optical characteristics such as the directional characteristics and the like may result in various variabilities, which are clumsy to use in the first conventional semiconductor light-emitting device 70.
Especially, when the semiconductor light-emitting device 70 is used as wavelength-converting typed semiconductor light-emitting devices, in which a part of the light emitted from the semiconductor light-emitting chip 83 is converted into light having a different wavelength by a phosphor contained in the first encapsulating resin 85 and in which a mixture light including the light having the different wavelength mixed with the light emitted directly from the semiconductor light-emitting chip 83 is emitted, the semiconductor light-emitting devices are usually provided with a wavelength converting material such as the phosphor in the first encapsulating resin 85. Therefore, the variability of the dome shape of the first encapsulating resin 85 may cause color variability in the mixture light, which is emitted from the second encapsulating resin 86 of the semiconductor light-emitting device 70.
Moreover, when a top surface of the semiconductor light-emitting chip 83 is formed in a rectangular shape, the uncured first encapsulating resin, which is dropped on the top surface of the chip 83 being formed in the rectangular shape, may flow from longer side surfaces in a longitudinal direction of the top surface of the semiconductor light-emitting chip 83 along the longitudinal side surfaces in advance of short side surfaces of the chip 83, and may spread under wet conditions on the die-bonding pad 81b of the first conductor pattern 81.
Accordingly, the uncured first encapsulating resin, which may spread under wet conditions on the die-bonding pad 81b of the first conductor pattern 81, may spread larger toward the longitudinal side surfaces than the short side surfaces. The first encapsulating resin 85, which should be formed in a dome shape, may be subject to a lopsided shape having a larger amount of the resin toward the longitudinal side surfaces. The optical characteristics of the device 70 may also cause the various variabilities, which are clumsy to use, because the dome shape of the first encapsulating resin 85 may be variable when the conventional semiconductor light-emitting device 70 is manufactured in a mass production process.
Applicant of this disclosed subject matter discloses a second conventional surface mount semiconductor light-emitting device, which may freely form the shape of the first encapsulating resin of the first conventional light-emitting device 70, and which is disclosed in Patent Document No. 2 (U.S. Pat. No. 8,115,106). FIG. 10 is an enlarged side cross-sectional view depicting the second conventional surface mount semiconductor light-emitting device disclosed in Patent Document No. 2 (U.S. Pat. No. 8,115,106).
The second conventional semiconductor light-emitting device 40 includes: a circuit board 47 having a first end and a second end including a first board 47a and a second board 47b; a first conductor pattern 41 including a first external electrode 41a and a die-bonding pad 41b, the first external electrode 41a formed underneath a bottom surface of the second board 47b of the circuit board 47, the die-bonding pad 41b formed on the second board 47b, exposed from the first board 47a of the circuit board 47 and being located in a middle portion of the circuit board 47, the first conductor pattern 41 connecting the die-bonding pad 41, surrounding the die-bonding pad 41b, and connecting from the die-bonding pad 41b toward the first external electrode 41a on the first board 47a and the second board 47b via the first end of the circuit board 47; a second conductor pattern 42 including a second external electrode 42a and a wire-bonding pad 42b, the second external electrode 42a formed underneath the bottom surface of the second board 47b and facing the first external electrode 41a underneath the bottom surface of the second board 47b of the circuit board 47, the wire-bonding pad 42b formed on the first board 47a of the circuit board 47, the second conductor pattern 42 extending from the wire-bonding pad 42b toward the second external electrode 42a via the second end of the circuit board 47 so that the first external electrode 41a does not contact with the second external electrode 42a; and wherein the first external electrode 41a of the first conductor pattern 41 and the second external electrode 42a of the second conductor pattern 42 are used to receive a power supply.
In addition, the second conventional semiconductor light-emitting device 40 also includes: a semiconductor light-emitting chip 43 having a top electrode and a bottom electrode mounted on the die-bonding pad 41b, and surrounded by the first conductor pattern 41, the bottom electrode thereof being electrically connected to the die-bonding pad 41b; a bonding wire 44 electrically connecting between the top electrode of the semiconductor light-emitting chip 43 and the die-bonding pad 42b of the second conductor pattern 41; a first encapsulating resin 45 encapsulating the semiconductor light-emitting chip 83 along with a contact portion between the top electrode of the chip 83 and the bonding wire 44; and a second encapsulating resin 46 encapsulating the first encapsulating layer 45 along with a part of the bonding wire 44 exposed from the first encapsulating resin 45.
Therefore, the second conventional semiconductor light-emitting device 40 can form favorable shapes of the first encapsulating resin 45 by laminating the first board 47a having an opening and the second board 47b as the circuit board 47. In addition, the light-emitting device 40 can improve reliability by providing a space between the first encapsulating resin 45 and the second encapsulating resin 46 even when each of thermal expansion coefficients of the first encapsulating resin 45 and the second encapsulating resin 46 differs. However, the circuit board 47 of the second conventional semiconductor light-emitting device 40 needs to laminate two boards.
The above-referenced Patent Documents are listed below, and are hereby incorporated with their English abstracts in their entireties.
1. Patent Document No. 1: Japanese Patent Application Laid Open JP2003-282952.
2. Patent Document No. 2: U.S. Pat. No. 8,115,106.
The disclosed subject matter has been devised to consider the above and other problems, features, and characteristics. Thus, embodiments of the disclosed subject matter can include small semiconductor light-emitting devices with a simple structure, in which a semiconductor light-emitting chip can be mounted on a circuit board without a laminate, and which can emit a wavelength converted light having excellent optical characteristics. The disclosed subject matter can also include a semiconductor light-emitting chip having a rectangular top and bottom surface that can be used for wavelength-converting light having the excellent optical characteristics.